The manufacture of polyurethane elastomers, whether rigid, or flexible, and whether the foam is microcellular or macrocellular, and whether the cellular structure is either open or closed, is widely known. Rigid foams are used for insulation and structural apparatus while flexible foams have wide usage in applications requiring cushioning. Cushioning applications are found in furniture, bedding and seats and other padded or cushioned interior for automobiles.
Polyurethane foams are prepared by reacting a polyisocyanate with a polyol and a crosslinker, typically an aromatic diamine or multifunctional, short chain polyol, with added fillers, catalysts and blowing agents. Rigid foams will require a higher level of crosslinking agent, while the flexible foams will have a lesser crosslink density than the rigid foams. Several properties are required in polyurethane systems for flexible foam, and include processing characteristics of the polyurethane system itself to permit handling, blending of the components, and filling of the mold. Efforts are continually being made to produce higher load bearing systems at equal density or equal load bearing at a lower density. In addition, fast demold and cycle times, reduced scrap, good tensile strength and so forth are required. To meet these requirements, crosslinkers have been used in various concentrations and types. One set of goals is to produce higher load-bearing, tear and elongation values. Other goals are to have material which can be blended easily and require little to no crushing when open cell structure is desired.
Representative patents which show the production of both rigid and flexible foams utilizing a polyisocyanate, polyol and aromatic diamines as a crosslinker, including alkoxylated aromatic diamines are as follows:
British Patent No. 1,398,185 discloses a process for producing flexible polyurethane foams by reacting a polyisocyanate with a polyol and a crosslinker system comprising an aromatic diamine/alkylene oxide reaction product. Toluenediamine/propylene oxide reaction products are shown. These aromatic amine/alkylene oxide reaction products increase the hardness of the resulting foam without consuming a substantial amount of isocyanate.
U.S. Pat. No. 3,580,869 discloses a process for producing microcellular polyurethane foams by reacting toluenediisocyanate with a polyol and an aromatic diamine, as well as, a propoxylated aniline.
U.S. Pat. No. 4,444,915 and U.S. Pat. No. 4,555,418 disclose a rigid polyisocyanurate foam prepared from a polyisocyanate, a polyol and an alkoxylated alkylamine as a crosslinking agent.
U.S. Pat. No. 3,948,825 discloses a process for producing cellular polyurethane foams which utilizes a conventional urethane formulation crosslinked with a system consisting of an alkylene oxide of methylene dianiline and more specifically an ethylene oxide/propylene oxide adduct of methylene dianiline.
U.S. Pat. No. 4,243,759 and U.S. Pat. No. 4,562,290 disclose the use of alkoxylated toluenediamines as a crosslinking agent for polyurethane foam systems. Ethylene oxide and propylene oxide adducts of toluenediamine are suggested as being suitable candidates for the crosslinking system.
U.S. Pat. No. 4,517,383 discloses a use of an alkylene oxide adduct of aniline for reducing viscosity of an polyurethane foam formulation.
U.S. Pat. No. 3,423,344 discloses a process for producing polyurethane polyol systems containing hydroxyalkylated polyamines which enhance the compressive strength and resistance to volume change under humid and dry aging conditions. The polyol component of the polyurethane formulation comprises a hydroxyalkylated polyamine formed by reacting ethylene or propylene oxide with an amine equivalent of a polyamine such as methylene dianiline and a polyol.
U.S. Pat. No. 4,235,977 discloses the use of an alkoxylated isocyanurate in preparing microcellular polyurethanes.